Effect of MgO on microstructure evolution and exothermic characteristics of tricalcium aluminate during hydration

The phase composition, microstructure, and hydration process of C 3 A with different MgO content were compared to elucidate the mechanism of hydration resistance of CaO improved by MgO–C 3 A solid solution . The process of hydration heat release was detected by isothermal calorimetry and the hydration products were analyzed by X-ray diffraction and scanning electron microscope. The results showed that the addition of MgO resulted in lattice distortion of C 3 A. In the middle and late stages of the hydration process, Mg(OH) 2 and amorphous gel-like substances covered the surface of the unreacted C 3 A and reduced the hydration reaction rate. The addition of MgO effectively reduced the hydration activity of the MgO–C 3 A solid solution that indicated the addition of MgO can improve the hydration resistance of CaO materials.